Defense doesn't mean not to start a war. Think about how Vietnam justified their invasion of Cambodia in 1978, or how China started the war with Vietnam the following year, or how Turkey entered Syria, how Pakistan fought the Taliban recently, and of course what Russia did in Ukraine, 2014 and 2022.

Wars are messy and have always been. Military actions are to be decided by the governments. Those who have resources are more willingly to use it, west or east.